In an electronic circuit apparatus for a compressor according to the related art, a circuit board having electronic parts soldered thereto is housed in a case, and four corners of the board are fixed to the case by fasteners, such as screws.
Hereinafter, a fixing method according to the related art will be described with reference to the accompanying drawings.
FIG. 4 is an exploded perspective view illustrating an electronic circuit apparatus according to the related art. In FIG. 4, case 10 is formed of synthetic resin, such as nylon or ABS resin, by injection molding, and opening 12 having a size that is slightly larger than that of board 20 is formed in case 10 such that board 20 can be housed in case 10.
A metal pattern (not shown) is formed on or in board 20, and electronic parts (not shown) are soldered to the metal pattern, so that board 20 has an electrical function. In addition, board 20 is provided with connectors 22 for electrically connecting the electronic parts (not shown) to the metal pattern. A portion of case 10 corresponding to connectors 22 is opened, thereby forming cord lead portion 15.
Holes are formed at four corners 25 of board 20 such that board 20 can be fixed to case 10 by board fixing screws 30. Holes are formed at four corners 17 of opening 12 of case 10 such that four corners 45 of lid 40 can be fixed to case 10 by lid fixing screws 50.
The operation of the electronic circuit apparatus for a compressor having the above-mentioned structure will be described below.
In an assembly process of the electronic circuit apparatus for a compressor, first, board 20 is inserted through opening 12 of case 10 such that connectors 22 can be electrically connected to an external apparatus through cord lead portion 15. Then, four corners 25 of board 20 are fixed to case 10 in the thickness direction of board 20 by board fixing screws 30. Finally, four corners 45 of lid 40 are fixed to opening 12 of case 10 by lid fixing screws 50, and board 20 is covered with case 10 and lid 40, thereby completing the assembly process.
This structure is disclosed in Japanese Patent Unexamined Publication No. 11-317570.
However, in the above-mentioned structure, when the electronic circuit apparatus for a compressor is turned on, stress is repeatedly applied to a soldering portion of the electronic part due to the difference between linear expansion coefficients of board 20 and case 10 that is caused by heat generated from the electronic part mounted on board 20 or a variation in the outside air temperature of case 10.
For example, it is assumed that the electronic circuit apparatus for a compressor is used in a temperature range of −50° C. to +90° C. in consideration of the use of the apparatus in the arctic area, the arrangement of the apparatus around the compressor, and heat generated from electronic parts. Therefore, when soldering strength deteriorates due to the stress applied to the soldering portion of the electronic part, soldering cracks may occur in the soldering portion of the electronic part, which results in a defective circuit.